1. Field of the Invention
The present invention relates to an ink housing container used for a printing apparatus ejecting a liquid to a print medium for printing.
2. Description of the Related Art
In recent years, ink jet printing apparatuses have been prevailing rapidly in which a print head ejects ink droplets to a print medium for printing. These ink jet printing apparatuses have the advantages of allowing the sizes thereof to be easily reduced and being capable of relatively easily performing color printing.
Some of these ink jet printing apparatuses include an ink tank serving as an ink housing container and from which ink is fed to the print head, which ejects ink to the print medium. With the ink jet printing apparatuses prevailing, the usage and production of ink tanks used for the ink jet printing apparatus have been increasing year by year. Many of such ink tanks are manufactured by filling resin into a mold tool for injection molding to form the resin into a predetermined shape and are adopted.
As described above, the ink tank in which ink is stored is often made of resin, generally. The resin used for the ink tank requires a high mechanical strength, a high chemical resistance, and an excellent gas barrier property. Thus, a recycled resin has not been used many times and a virgin resin has often been used to manufacture ink tanks.
However, much effort has been made to develop universal design throughout the world. Based on the concept of the universal design, industrial products are manufactured with visibility and ease of use taken into account. Thus, the design of products with user friendliness taken into account has been more important. Based on the concept of the universal design, some ink tanks are formed such that an outer layer of the ink tank composed of multiple layers is partly colored in the same color as that of the ink housed in the ink tank, and such ink tanks are adopted. Such a type of ink tank is formed of, besides the virgin resin, a resin colored in the same color as that of the ink. The ink tank thus formed serves to improve the visibility of the color of the ink inside the ink tank, allowing the user to easily determine the color of the ink housed inside the ink tank. Thus, at present, many ink tanks are composed of a plurality of layers including a layer formed of the virgin resin and a colored layer.
Furthermore, much attention has recently been paid to makers' approaches to environmental problems. Thus, for the manufacture of ink tanks, various attempts have been made to manufacture products taking the environmental problems into account. As part of approaches to the environmental problems, efforts have been made to develop a closed recycling involving the production, sale, collection, and reutilization of products. This allows the materials of the products to be reutilized. As described above, the ink tank may be molded using a recycled resin so that the resin forms a part of the ink tank.
In connection with an environmentally friendly ink tank, Japanese Patent Laid-Open No. 2006-159097 discloses a method for molding an ink tank using a recycled resin. The method for molding the ink tank disclosed in Japanese Patent Laid-Open No. 2006-159897 uses a multilayer injection compression molding method to form at least one layer of a molding target member using the recycled resin.
Japanese Patent Laid-Open No. H8-187871 (1996) discloses an ink tank including an outer wall partly formed of a recycled resin. In the ink tank disclosed in Japanese Patent Laid-Open No. H8-187871 (1996), a portion of the ink tank contacting with the internally stored ink is formed of an unused, virgin resin. The outer wall portion not contacting with the ink is formed of the recycled resin. The ink tank formed partly of the recycled resin is manufactured while maintaining resistance to ink.
The ink tank manufacturing process described above requires consideration for the adverse effect, on the quality of the ink, of the contact of the ink with the ink tank, causing the resin component of the ink tank to be eluted into the ink. When the ink is stored inside the ink tank formed of a resin failing to resist ink, the resin component may be eluted into the stored ink. This may change the components of the ink.
Furthermore, if the resin forming the ink tank offers an inadequate gas barrier property, air entering the ink tank may change the components of the ink. The thus changed characteristics of the ink may degrade the quality of the ink.
Thus, a portion of the ink tank in which the ink is stored needs to be formed of a material that resists ink and prevents air from entering the ink tank. Thus, when an ink tank is formed using both an unused, virgin resin and a colored or recycled resin, the portion of the ink tank in which the ink is stored needs to be formed of the virgin resin. A portion of the ink tank which does not contact with the ink may be formed of the colored or recycled resin.
An example of the conventional ink tank manufacturing process disclosed in Japanese Patent Laid-Open Nos. 2006-159097 and H8-187871 (1996), described above, will be described with reference to FIGS. 19 to 22A and 22B. As shown in FIG. 19, an ink tank 101 as an ink housing container has a cover member 111 and an ink container 120 as a container member. The ink container has two resin layers, an inner layer 121 and an outer layer 122.
FIG. 19 is a sectional view of the conventional ink tank. Ink is stored in the inner layer 121 of the ink container 120, formed of the two layers. Thus, the inner layer 121 is formed of a material that resists ink and prevents air from entering the ink tank. The outer layer 122, covering the outer periphery of the inner layer 121, is formed outside the inner layer 121.
FIG. 20A shows a primary molding step of the manufacturing process for the ink container 120 of the ink tank 101 shown in FIG. 19. Here, the primary molding is a step of forming the inner layer 121 of the ink container 320 by means of molding. In the primary molding, a movable mold 160 and a first fixed mold 161 are used as a mold tool for molding the ink container 120. As shown in FIG. 20A, a first resin 21-a is infected between the movable mold 160 and the first fixed mold 161 by an injection cylinder 163. At this time, a clamping force is held between the movable mold 160 and the first fixed mold 161. Thus, the first resin 21-a is filled under pressure. Then, the mold tool is cooled with the pressure maintained to solidify the first resin 21-a. The inner resin 121 is thus formed.
FIG. 20B is a sectional view of the end of a side wall portion of the inner layer of the ink container 120 formed by the primary molding. As shown in FIG. 20B, a side surface is formed on a side wall of the inner layer 121 so as to extend substantially perpendicularly from a surface of the cover member-side end thereof which surface contacts with the cover.
The step shown in FIG. 21A is carried out between the primary molding and secondary molding described below. With the inner layer 121 formed by the primary molding attached to the movable mold 160 without being separated therefrom, the movable mold 160 moves to a position corresponding to a second fixed mold 162. Thus, the mold located at the position corresponding to the movable mold 160 changes from the first fixed mold 161 to the second fixed mold 162. At this timer a space is provided between the inner layer 121 and the second fixed mold 162 so that a resin forming the outer layer described below is positioned in the space. In this case, while the first molding step is shifting to the secondary step, the inner layer 121 is cooled and shrunk in the directions of arrows shown in FIG. 21A.
FIG. 21A, the lengths of the arrows correspond to the amounts of shrinkage. The shrinkage amount of the resin is proportional to the thickness of the molded resin. Thus, in the ink container in this example shaped as described above, the side wall 125 shrinks more significantly in the height direction from the bottom surface of the ink container 120 than in the thickness direction of the side wall 125. In this case, for the shrinkage of the side wall 125 in the height direction thereof, the amount of change corresponding to the shrinkage is manifested at the end of the side wall 125 because the bottom surface 124 is in contact with the movable mold 160. FIG. 21B shows the end of the inner layer 121 in this case. As described above, the shrinkage of the inner layer 121 results in a gap 165 between the movable mold 160 and an ink container-side coupling portion 123 that is a surface of the inner layer contacting with the cover member 110.
When the movable mold moves from the position corresponding to the first fixed mold 161 to a position corresponding to the second fixed mold 162, secondary molding is performed by injecting a second resin 22-a used to form an outer layer, into the space between the inner layer 121 and the second fixed mold 162, as shown in FIG. 22A.
At this time, the resin may flow into the gap 165, which is present between the inner layer and the movable mold and which has been formed between the primary molding and the secondary molding by the shrinkage of the inner layer 121 resulting from the solidification thereof. FIG. 22B is a sectional view of the end of the ink container formed by the resin flowing into the gap 165. The resin used for the primary molding is assumed to be used for the inner layer, which contacts with the ink. The resin is thus secured ink resistance and a gas barrier property. The resin is further secured a proper bonding strength with respect to the cover member 110. However, the resin used for the secondary molding is used to form the outer layer 122 and may thus fail to secure a proper bonding strength and sufficient closeness. Consequently, when the resin filled during the secondary molding flows into the gap 165, the resin for the secondary molding is present between the cover member 110 and the ink container 120. This may prevent a portion requiring a high bonding strength and high closeness from offering these properties.
Furthermore, in FIGS. 22A and 22B, the second resin 22-a is filled up to the inner end of the gap between the movable mold 160 and the inner layer 121. However, since the gap is a relatively narrow area, when the second resin 22-a flows through the gap, a relatively large flow resistance occurs in the second resin 22-a. Thus, even when the second resin 22-a is filled between the movable mold 160 and the second fixed mold 162 under pressures the second resin 22-a may stop flowing before reaching the inner end of the gap. In this case, the resin may not be in part of the gap to form a recess and a protrusion in an area in which the ink container 120 and the cover member 110 are in contact. This may make the coupling area between the ink container 120 and the cover member 110 insufficient. Consequently, the coupling portion may fail to offer a sufficient strength. Furthermore, the recess and protrusion in the area in which the ink container 120 and the cover member 110 are in contact may prevent high closeness from being maintained between the ink container 120 and the cover member 110.
As described above, in the conventional ink tank 101, the cover member 110 and the member forming the ink container 120 of the ink tank 101 may be improperly coupled together or insufficiently closed. Moreover, if a recycled resin is used to form the outer layer 122, the recycled resin may flow to the inner layer side of the ink container 120 and come into contact with the stored ink. Then, the resin may be eluted, thus changing the characteristics of the ink stored inside the ink tank. A similar problem may occur with the cover member 110, which is a component of the ink tank 101 other than the ink container 120, if the second resin flows to the inner side.